Paper manufacture



11 QFFICE Harold Robert ton, Andover, Mass,

to Raii'old Process Corporation, a co war-aha of Massachusetts No Drawing.

Serial No.

1933; Serial No. 672,901

This invention concerns the manufacture of paper containing alkaline filler.

This is a division of my copending application Serial No. 534,462, filed May 1, 1931, now matured into Patent No. 1,914,526, issued June 20, 1933.

The principal object of this invention is to provide a method whereby a material chemically incompatible with alkaline filler, such as acidic material, may retain its effect in a paper containing alkaline filler.

A further object is to prepare substantially foam free paper containing alkaline filler.

A further object is to provide a method for the production of sized paper containing .1 filler.

Other objects and advantages of this invention will become apparent during the course of the following description.

In my copending applications Serial No. 304,- 167, filed September 5,1928, now matured into Patent No. 1,803,642, issued May 5, 1931, and Serials No. 321,753 and No. 321,754, both filed November 2 1, 1928, now matured into Patents Nos. 1,808,070 and 1,808,071, respectively, both issued June 2, 1931, I have described methods. whereby both sized and unsized paper filled with an alkaline filler may be made by the addition of an alkaline filler to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix. In various other of my copending applications I have also described methods whereby alum, size, and other ingredients may similarly be added. The principle on which materials are so added to a paper mix has been thoroughly discussed in my copending applications, and briefly summarized, may be described as being based on the fact that alkaline filler which alwaysis present in the stock from which paper filled with line filler is e in great stoichiometric'al excess over the acidic constituent, acts upon the acidic constituent to the ultimate destruction thereof and/or the destruction of the efiect maintained by such con- 45 stituent. (The acidic constituent so-called may be one which is actually acid and/or one which such as a size precipitate is capable of being affected or deteriorated by an alkaline filler.) The action just referred to has been found to depend upon the time of contact of the acidic and alkaline constituents and also upon the intirnacy of contact of these constituents. Agi

tation such as no'mally occurs, in papermaking procedure in stufi chests, or the like, accelerates the rate of reaction, but agitation at low concenstock from the machine chest, after which point @riginal application May 1, 1931, 534,462. Patent No. 1,914,526, June 20, 1933. Divided and this application May 25,

(ill. 92-21) trations while having some effect is not near so deleterious. 1 Based on this principle the practical adaptations thereof disclosed in my copending applications have been developed whereby, by minimizing the time and/or intimacy of contact of the alkaline and acidic constituents, the acidic constituent and/or the efiect produced thereby is substantially preserved in an alkaline filler mix. With the present types of paper machines and the present arrangement of apparatus employed in paper machine operation, the contact'of the acidic material and the alkalineconstituent at any time prior to the passage of the stock from the last stuff chest, which is commonly called the machine chest, results in great deterioration or complete destruction of the acidic material. Addition of one or both oftheseconstitucuts at a point subsequent to the e of the according to present day operating practice the stock remains in concentrated condition only for a very brief interval of time, or additionprefer-I ably at or subsequent to the point of dilution, i. e. at the wet end of the paper machine, serves to substantially conserve the acidic material and/or efi'ect thereof in the fibrous mix.

In my copending application Serial No. 501,674, filed December 11, 1930 now matured into Patent No. 1,922,325, issued August 15, 193-3, I have disclosed that satisfactory sizing may be obtained in a paper containing alkaline filler, providing that the introduction of a size precipitate is effected in the forming web or in the already formed web. This is preferably accomplished on by addition of size and/or size precipitant at a suitable point on the paper machine. As will be understood this is in harmony with the general principle set forth above, as the time of contact of the acidic and alkaline constituents of the paper in the wet condition is thereby greatly minimized: and although the intimacy of contact is not diminished, its effect is by the fact that there is practically no agitation of the constituents with respectto one another except at the beginning of the web formation, and as such agitation takes place in relatively dilute suspension its effect is relatively slight.

I have also found that instead of the introduction in the paper -web of the size and/or size precipitant as described in my above cited copending application, I may with great advantage introduce other materials in the web, particularly alkaline filler. The acidic constituent may be introduced previously into the. paper mix, or may issued May 5, 1931.

be simultaneously introduced in the web with the alkaline filler or may be applied to the web previously or subsequent thereto, but in any case the conditions obtaining are as explained above, such that the acidic material and/or effect produced thereby is substantially undeteriorated by the alkaline filler, though the alkaline filler is present in great stoichiometrical excess over the acidic constituent.

If I desire to make substantially unsized paper containing alkaline filler, the preferred practice of my invention is as follows: I first prepare in the customary apparatus a paper mix containing suitable fibrous ingredients together with alum. The alum may be present in an amount governed by the quality of the paper to be made and machine conditions, but in general, while I do not restrict myself thereto, approximately 2% on the dry weight of the furnish will be found to be suitable. Under some conditions the alum may be added in the beater but if there be present in the fibrous constituents alkaline filler, this will cause the destruction of the alum, and under these conditions, it is preferable to add the slum at the wet end of the paper machine as set forth in my copending application Serial No. 304,171, filed September 5, 1928, now matured into Patent No. 1,803,646, issued May 5,1931. The paper mix containing alum is led to the web-forming device of a paper machine, and on the web-forming device by any suitable known means alkaline filler is introduced into the web, or alkaline filler may be applied to one or both sides of the web by suitable known means at the presses or elsewhere on the machine before the paper is completely dried. In the latter instance the alkaline filler will penetrate the web to some extent but will not be substantially uniformly distributed throughout as will be more nearly the case it it is added during the course of web formation. The

amount of alkaline filler which maybe intro alkaline filler, the preferred. practice of my invention is as follows: 1 prepare a paper mix in the customary apparatus with fibrous material. size, and alum in the usual manner, and lead the "mix to the web-forming device. On the webforming ,device or subsequent thereto, as explained above, alkaline filleris added. If there be alkaline. filler in the fibrous material employed, the process disclosed in my copending application Serial No. 304,168, filed September 5, 1928, now matured into Patent No. 1,803,643, issued May 5,1931, may be used to restore the deteriorated size precipitate by the addition of alum at 'the wet endof the paper machine, or the alum,

or alum and size, may be added at the wet end of the paper machine as disclosed in my copending application Serial No. 304,172, filed September 5, 1928, now matured into Patent No. 1,803,647, By these procedures sub stantially undeteriorated sizing will be present in the paper mix fed to the web-forming device.

Several alternative modifications may be used in connection with this form of my invention, e. g. the alum alone may be added in the paper mix and the size and the alkaline filler added on the paper machine thereafter, or size alone may be added in the fibrous mix and alum and alkaline filler added on the paper machine thereafter, or if desired, both the alum and size, or precipitated sizing, and alkaline filler may be added on the paper machine.

The amounts of size and alum used will be substantially the amounts normally used in sizing papers containing filler, and as will be apparent will vary with degree of sizing desired, nature of fibrous materials, machine conditions, and the like, but in general, while not limiting my practice in any way thereto, it will be found that approximately 2% size and 3% alum on the weight of the furnish will be suitable. The size and alum may be applied by suitable applying devices such as sprays, applying rolls, or the like. The mattery of applying size and size precipitant on the paper machine has been fully discussed in my copending application Serial No. 501,674 cited abovefand reference is made thereto in this connection.

Where more than one constituent is to be added on the paper machine, 1. e. where for example alkaline filler, size and/or alum are to be added, it is suitable to mix the alkaline filler with the size and. add this mixture as this provides one less ingredient to be handled. Where alkaline filler and alum are both to be added, these may be added mixed together, but in such case the mixture should take place immediately before the addition of the alkaline filler, a suitable method for-this and the reasons therefor being described in my copending application Serial No. 428,231 filed February 13, 1930 now matured into Patent No. 1,879,483, issued Sept. 27, 1933, to which reference is hereby made. Also both the size and the alum may be added to the alkaline filler, but here again the alum must be added just before the alkaline filler is utilized in order not to deteriorate substantially the size precipitate, and in this connection cross reference is hereby made to my copending application Serial No. 533,571, filed April 28, 1931 now matured into Patent No. 1,898,098, issued February 2, 1933, wherein a method of preparing a so-called temporarily protected alkaline filler for immediate inclusion in a paper mix is disclosed. Likewise precipitated and alkaline filler may be added premixed.

In practicing my invention, the alkaline filler is suitably added continuously and proportionately in water suspension, at a concentration which may vary with conditions, but which may conveniently be 1 to 3 lbs. per gallon. Alum and/or size when employed on the paper machine may likewise be added continuously and proportionately in solution. for example, alum suitably at about 2% concentration, while a similar concentration of size solution or emulsion is convenient. 1

The types of paper machines widely employed at the present time are the so-called Fourdrinier and cylinder machines. The Fourdrinier machines are normally employed for the better grades of paper whereas the cylinder machines are employed on the less expensive grades, espe- 'cially for the manufacture of multi-ply paper.

broad stream from a known device placed across and above the web,-but it is most suitably effected in the vicinity of the first suction box. Here the web is still in relatively fluid condition, and at this point a filler may be introduced and incorporated with reasonable uniformity throughout the web with however but little passing into the white water. The amount of filler may be regulated as desired. The application of the filler after web formation to the already formed web may take place suitably on the press rolls or smooth rolls of the machine. Known devices are available which may be used for applying the filler at these points.

If a cylinder machine be employed with the common type of cylinder where the only suction is that induced by gravity, the alkaline filler may be introduced on the surface of the web on the cylinder, or on the surface of the web after it has left the cylinder, by a device similar to that mentioned in connection with the Fourdrinier machine above. If multi-ply paper is being produced, the alkaline filler may suitably be introduced between two or more plies, and/or if desired on one or more of the outer surfaces of the multi-ply paper. It is of course apparent that only one ply, or a selected numberof plies, of a multi-ply sheet may have alkaline filler applied thereto or in. Application of alkaline filler later on a cylinder machine may take place as on a Fourdrinier machine, as explained above.

There have recently come into commercial use several other types of paper machines with which the practice of my invention is particularly suitable. In connection with certain heavy,-paper or board machines, it is now customary to use a rotary suction filter for the web-forming element. In such case, the continuous application of a thin transverse stream of alkaline filler, particularly to the web on the surface of the filter, preferably a short-time after the web leaves the liquid stock 'in the filter tank, at which point the suction is preferably still being applied to the web, serves to incorporate the alkaline filler satisfactorily into the web without substantially drawing it through into the white water.

There is another general type of paper machine, somewhat similar to the. Fourdrinier machine, which has been recently developed to a commercial basis. Examples are the so-called Millspaugh machine and others of analogous construction. The web-formingelement of such machines comprises substantially a suction roll over an arc of the surface of which runs a short Fourdrinier wire or other web conveying means. The paper mix is fed by a suitable device such as an inlet or headbox on to the surface of the wire at a point where the wire contacts with the suction roll, and the suction of the suction roll causes 'a continuous web to form on the moving wire. The web is subsequently removed from the wire usually by a second suction roll, over which may suitably run a conveying felt. There is usually more than one suction compartment in the forming suction roll and where this type of machine is used with my invention, it is suitable to apply the alkaline filler either after the formation of the web at a point over the first suction chamber, or over the second suction chamber. Any suitable device for introducing the alkaline filler to the web at this point may be used, suitably a second head or feed box spacedly disposed from the first. It will be recognized that the suction chamber or chambers of the suction roll on this type of machine act promptly to form the sheet and dewater it, so that a slight change in the point of application of the alkaline filler may change considerably the depth of penetration of the alkaline filler into the web.

I prefer to add the alkaline filler on the web at a point where substantiallyno alkaline filler will be drawn into the white water coming from the machine, i. e. where substantially all of it will be filtered out by the web, in order that substantially no alkaline filler may be mixed with the white water, which is returned to the stock system, and thus be mixed with the stock to be fed into the machine. However if desired, especially in the case where an alkaline filler paper mix is being run on the machine, the white water of such alkaline filler mix may be used as part or the entire source of alkaline filler to be introduced in the forming or already formed web.

Such paper machines as referred to above may operate as individual machines, or as multi-ply machines, combining the webs either wire to wire side, top side i. e. felt side to felt side, or felt side to wire side, as desired. The individual or combined webs may then be treated on presses and driers substantially as on the ordinarytype of papermaking machines. It is apparent that my invention may be practiced either on the webforming device or later with this type of machine, just as with the more common types of paper machines. Y i

It will thus be apparent that the application of my invention is not limited to any specific type of papermaking machine, and the illustrative examples noted above will enable one skilled in the art to apply it to any type of papermaking machine now existing. or which may be developed.

It is of course apparent that if desired fibrous material may be admixed with the alkaline filler in its incorporation into or application to the web. Such fibrous material may, in certain cases where it is not desired to introduce alkaline filler into the paper mix feeding the paper machine, comprise alkaline filler containing fibrous material such as the trim and/or efliuents and/or broke from the paper machine, such broke being suitably defibred and diluted prior to admixture with the alkaline filler. I

It is apparent from the above description that several varieties of paper may be produced in the practice of my invention. In the first place either a sized or unsized paper, filled with alkaline filler distributed substantially or reasonably uniformly throughout, may be produced, which is very similar to paper filled with alkaline filler, produced by addition of alkaline filler to the paper mix. On the other hand where the alkaline filler is added to the already formed web, the paper produced will naturally have a concentration of filler on one of its surfaces if filler is applied to only one surface, or a concentration of filler on both surfaces if the filler be so applied. If the amount of filler applied to the surface be relatively a small percentage by weight in comparison with the total furnish, satisfactorily sized papers may be produced. But it will be evident as the concentration of the filler increases on the surface, that the sizing will be relatively poorer, except in such instances as noted above where sizing is actually incorporated into the web on the machine along with the alkaline filler.

However the introduction of the filler on the surface of the web, or the introduction of the filler with fibre on the surface of the web, serves a very useful purpose in one adaptation of my invention. For example a sized stock which is being run on a machine may have a substantial layer of alkaline filler or alkaline filler and fibre applied to the already formed web, and a similar web from another web-forming device may be joined therewith, suitably filler side to filler side, that is, felt side to felt side, and the two webs joined as usual on multi-ply paper machines. The result may be a multi-pLv sized paper: filled with alkaline filler with the two wire sides outermost, the wire sides thus being adequately sized for the purpose intended whereas the innerlayer of filler, or filler and fibre may be substantially unsized. Thus a multi-ply paper may be produced employing alkaline filler, wherein no alkaline filler or paper machine effluents, wastes or broke containing alkaline filler or broke need come into contact with or be associated with the sized fibrous mix, as such wastes may suitably be diverted to and, admixed with the alkaline filler applied continuhusly to the web surface.

On the other hand, the process may be reversed and two webs, each having alkaline filler on one side, may be united with the wire sides together, in which case of course very. different surface characteristics may be obtained, but in general the sizing will not be so hard in such papers as in the papers where the felt sides are united.

Another adaptation of my invention is where ,on a multi-cylinder or other multi-web-forming machine, alkaline filler-fibre mixes, substantially unsized if desired, may be run as the interior ply or plies of a multi-ply sized sheet. This constitutes another means of applying alkaline filler to a web, in this case as an interposed layer, the alkaline filler-fibre layer or web being combined with the sized fibre web in the customary manner. Then the broke and machine wastes or effluents may be returned to the feed for the alkaline filler ply or plies and the sized fibrous plies may therefore be made free from alkaline filler, or alkaline filler-containing materials if desired. In this adaptation, the resulting paper may have one or both outside plies sized, producing suitably in the former case a paper sized on one side, and in the latter, on both.

Another variation of this procedure, particularly adapted to the Millspaugh type machine, is to run the alkaline filler-fibre mixture asthe main web and superpose a sized fibrous layer on top on suitably the same forming wire from a second head or feed box, This, as will be readily appreciated, constitutes the introduction of alkaline filler in a forming or on a formed web, only in this case the alkaline filler is "subposed rather than superposed on the sized web.

As will be apparent any suitable combinations of the above described variations of my invention may be employed.

In connection with the invention disclosed herein cross reference is hereby made to several other of my copending applications, not hitherto referred to herein, as follows: Serial No. 304,174, filed September 5, 1928, now matured into Patent No. 1,803,649, issued May 5, 1931; Serial No. 325,405, filed December 11, 1928, now matured into Patent No. 1,812,832, issued June 30, 1931; and Serial No. 426,189, filed February 5, 1930, now matured into Patent No. 1,834,903, issued December 1, 1931.

I am aware that it has been previously proposed to add filler to the forming or already formed web, and that devices exist by which this may be suitably accomplished. However it has not hitherto been recognized that it is possible to apply these procedures to alkaline fillers because of the known incompatibility of alkaline fillers with acidic constituents. It is only by applying the previously explained concept of minimizing the time of contact of the alkaline filler with the acidic constituents of the web that the practice of this procedure has been made available in the use of alkaline filler, contrary to the hitherto supposed limitations thereon.

It will be further noted that another limitation previously imposed on such practices of so employing alkaline filler was the disposal of the machine efiluents and/or wastes containing alkaline filler. Such wastes, the same as alkaline filler itself, are incompatible with acidic materials in paper mixes and will destroy the same when mixed with them in the furnish, as they would be in a mill operation conducted in the customary manner. By the various cycles described herein it will be seen that such emuents.

web, which practice produces a highly practical solution of this hitherto diiiicult problem.

It will be apparent also, according to the general principle set out herein, that alum may suitably be added on the paper machine during or after web formation to a web made from a paper mix containing alkaline filler.

For size I may use rosin size, or any size which may be used as a substitute therefor in' the paper industry, such as saponified fatty acids or the like, or emulsions of various materials such as paraffin, or emulsions of other materials which may, for example, be substantially unaffected by alkaline filler.

Instead of alum, with a certain measure of success, I. may use alone or in combination acidic materials, such as a mineral or other acids, particularly metallic salts such as compounds of aluminum, zinc, tin, or the like.

The term paper mix" as used herein is intended to mean a mix of various constituents including fibre from which paper may be made, either alone or after the addition of. other ingredients.

By the term alkaline filler I mean substantially water insoluble filler which when agitated in contact with freshly boiled distilled water, say for an hour, will impart a pH value to such water greater than 7.0, that is, which will be on the alkaline side of the neutral point. Among fillers included in this group may be mentioned calcium carbonate, of which lime mud from the causticizing process is one form; calcium carbonate magnesium basic carbonate employed in the paper disclosed in my United States Patent No. 1,595,416 of August 10, 1926; calcium carbonate magnesium hydroxide disclosed in my United States Patent No. 1,415,391. of May 9, 1922; and other substantially water insoluble normal or basic carbonates of alkaline earth metals, (which expression is herein intended to include magnesium), or compounds, double salts, or physically associated mixtures of these with one or more other acid soluble materials of a substantially water insoluble nature.

When I use the word paper herein, I use it in the broad sense to include products of manufacture of all types and of all weights and thicknesses, which contain as an essential constituent a considerable amount of prepared fibre and which are capable of being produced on a Fourdrinier, cylinder, or other forming, felting, shaping or molding machine.

When I use the expression wire side, I use it in the ordinarily accepted papermaking sense of the term to meanthat side of the web which has been adjacent the web-forming means, i. e. .the wire cloth or other means serving the equivalent purpose.

6 By the term wet end of the paper machine",

I intend to include those instrumentalities employed in paper manufacture by which and/or in which a relatively concentrated paper mix is diluted, and treated, conveyed or fed up to the point of web-formation, such as the mixing box, regulating and proportioning devices, riillers, troughs, screens, head boxes, inlets and the like, including also instrumentalities used in the white water cycle.

Where in the claims I use the word web, I mean to include not only the already'formed web, after it has left the web-forming device, but also the forming web as it exists at any point on the web-forming device.

Where in the claims I use the word "adding in reference to alkaline filler and/or other materials (such as size, alum, fibre and the like) and a,

paper web, I mean the process of including an already existing alkaline filler such as described in detail above and/or other materials in the forming web and/or applying it or them to the surface or surfaces of the formed web, on a paper machine prior to the completion of the drying of said web.

It is to be understood that my invention is not dependent upon or limited by any theory expressed herein.

While I have described in detail the preferred embodiments of my invention, it is to be understood that the details of procedure, the proportions of ingredients, and the arrangement of steps may be widely varied without departing from the spirit of my invention or the scope of the subjoined claims.

I claim:

1. The steps in a method of manufacturing paper containing alkaline filler comprising preparing a paper mix containing alkaline filler, delivering said mix to a web-forming device, forming a web and adding acidic material thereto.

2. The steps in a method of manufacturing paper containing alkaline filler comprising preparing a paper mix containing alkaline filler, delivering said mix to a web-forming device, forming a web and adding metallic salt thereto.

3. The steps in a method of manufacturing paper containing alkaline filler comprising preparinga paper mix containing alkaline filler, delivering said mix to a web-forming device, forming a web and adding alum thereto.

4. The steps in a method of manufacturing paper containing calcium carbonate comprising preparing a paper mix containing calcium carbonate, delivering said mix to a web-forming device, forming a web and adding acidic material thereto. a

5. The steps in a method of manufacturing paper containing calcium carbonate and magnesium compound comprising preparing a paper mix containing calcium carbonate and magnesium compound, delivering said mix to a webforming device, forming a web and adding acidic material thereto.

6. The steps in a method of manufacturing paper containing calcium carbonate magnesium hydroxide comprising preparing a paper mix containing calcium carbonate magnesium hydrox ide, delivering said mix to a web-forming device, forming a web and adding acidic material thereto.

'7. The steps in a method of manufacturing paper containing alkaline filler comprising preparing a paper mix containing alkaline filler, delivering said mix to a web-forming device, forming a web and adding acidic material to said web prior to the passage of said web from said web-forming device. 8. The steps in a method of manufacturing paper containing alkaline filler comprising preparing a paper mix containing alkaline filler, delivering said mix to a web-forming device, forming a web and adding metallic salt to said web prior to the passage of said web from said webforming device.

9. The steps in a method of manufacturing paper containing alkaline filler comprising preparing a paper mix containing alkaline filler, delivering said mix to a web-forming device, forming a web and adding alum to said web prior to the passage of said web from said web-forming device.

10. The steps in a method of manufacturing substantially unsized paper containing alkaline filler comprising preparing a paper mix containing alkaline filler, delivering said mix to a webforming device, forming a web and adding acidic material thereto.

11. The steps in a method of manufacturing substantially unsized paper containing alkaline filler comprising preparing a paper mix containing alkaline filler, delivering said mix to a webforming device, forming a web and adding metallic salt thereto.

12. The steps in a method of manufacturing substantially unsized paper containing alkaline filler'comprising preparing a paper mix containing alkaline filler, delivering said mix to a webforming device, forming a web and adding alum thereto.

13. The steps in a method of manufacturing substantially unsized paper containing alkaline filler comprising preparing a paper mix containing alkaline filler, delivering said mix to a webforming device, forming a web and adding acidic material to said web prior to the passage of said web from said web-forming device.

14. The steps in a method of manufacturing substantially unsized paper containing alkaline filler comprising preparing a paper mix containing alkaline filler, delivering said mix to a webforming device, forming a web and adding metallic salt to said web prior to the passage of said web from said web-forming device.

15. The steps in a method ofmanufacturing substantially unsized paper containing alkaline filler comprising preparing a paper .six containing. alkaline filler, delivering said mix to a webforming device, forming a web and adding alum to said web prior to the passage of said web from said web-forming device.

16. The steps in a method of manufacturing substantiallyunsized paper containing calcium carbonate comprising preparing a paper mix containing calcium carbonate, delivering said mix to a web-forming device, forming a web and adding acidic material to said web prior to the pasadding acidic material to said web prior to the passage of said web from said web-forming device."

18. The steps in a method of manufacturin substantially unsized paper containing calcium 20. The method of manufacturing substan-- tially unsized paper filled with alkaline filler, wherein acidic material is added to the paper mix under conditions favoring the minimizing of the time of contact of the constituents of the mix, comprising mixing fibrous material, alkaline filler, and acidic material, forming a web from the resulting mix, and applying acidic material to said web.

21. The method of manufacturing substantialprising mixing fibrous material, calcium carbonate, and alum, forming a web 'from the resulting mix on a web-forming device, and applying alum to said web prior to the passage of said web from said web-forming device.

22. The method of manufacturing substantially unsized paper filled with alkaline filler, comprising mixing fibrous material, alkaline filler, and acidic material, said acidic material being added at the dilute stage of the papermaking operation, forming a web from the resulting mix, and applying acidic material to said web.

23. The method of manufacturing substantially unsized paper filled with calcium carbonate, comprising mixing fibrous material, calcium carbonate, and alum, said alum being added at the dilute stage of the papermaking operation, forming a web from the resulting mix on a webfomiing device, and applying alum to said web prior to the passage of saidweb from said webforming device.

HAROLD ROBERT RAFTON. 

